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(No Model.) 2 Sheets-Sheet 1.

W. W. 8v J. B. PRIMM.

BALANGED SLIDE VALVE..

(No Model.) 2 Sheets- Sheet 2.

W. W. 8v J. B. PRIMM v BALANOED SLIDE VALVE.

N0. 361,647. Patented Apr. 19, l1887.

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NITED STATES PATENT ENCE. i

VILSON W. PRIMM AND JEAN B. PRIMM, OF ST. LOUIS, MISSOURI, ASSIG- ORS OFONE-THIRD TO SARAH L. PRIMM, OF SAME PLACE.

BALANCED SLIDE-VALVE..

SPECIFICATION forming part of Letters Patent No. 361,647, dated April19, 1887.

' Application tiled December 30, 1886. Serial No. 223,009. (No model.)

.To all whom it may concern.-

Be it known that we, WiLsoN W. PRIMM and JEAN B. PRIMM, citizens of theUnited States, residing at the city of St. Louis, State of Missouri,have invented a certain new and useful Improvement in BalancedSlide-Valves for Steam-Engines, of which the following is a full, clear,and exact description.

Our invention relates to improved means of balancing the slide-valves oflocomotive and other steam engines, and it consists in thecombination,with a slide-valve and its steam-chest and abalancing-piston connected with the slide-valve, of a pipe or passagecommunicating with the piston-cylinder and with the atmosphere, a pipeor passage communicating with the steam-chest and with the atmosphere,and

l a three-way valve controlling both pipes or passages, whereby steammay be admitted to the piston-cylinder and air to both cylinder andsteam-chest at will.

It also consists in the combination, with a slide-valve andbalancing-piston, of a port or passage leading from the exhaust-passageto the cylinder of the balancing-piston and a loaded valve forcounteracting the effect of varying back-pressure on the slide-valve.

It also consists in minor details of construction, which willhereinafter more fully appear.

On the accompanying drawings, Figure 1 is a longitudinal section of theslide-valve of a steam-engine fitted with our invention; Fig. 2, atransverse section of the same; Fig. 3, a part plan thereof; and Fig. 4,a transverse section showing additional features of our invention asapplied to locomotive slide-valves, or where varying backpressure on theslidevalve has to be counteracted, like letters of reference denotinglike parts in all the figures.

Referring particularly to Figs. 1 to 3, a represents a slide-valve, andZ) the steam-chest, in the cover c of which is a cylinder, d, ofsuitable area, as hereinafter more particularly referred to, and openingat one end into the steam-chest b. In the cylinder d is fitted a piston,e, connected atits inner or under side, nearest the steam-chest b, tothe top of the slide-valve a by a connecting-rod, f, the steam from thesteam-chest b pressing against the under side of the piston e, andthereby counterbalancing the downward pressure on the slide-valve a.

As shown in Figs. 1 to 3, the rod or pin g, which couples theslide-valve a to the connecting-rod f, extends entirely across the topof the slide-valve a and has its bearings in four lugs, 72, the bolts ofwhich pass through the top of the slide-valve a, and are secured thereatby nuts screwed against packing-strips i, of wrought-iron or othersuitable material, in-` terposed between the nuts and the under side ofthe slide-valve a, this arrangement being particularly intended for theapplication of our invention to existing slide-valves; but in the caseof new valves the lugs h may be cast on the slide-valve a without thenecessity of the bolts, nuts, and packing-strips, as shownv in Fig. 4.

The outer or upper end of the cylinder d is closed by a cover, j, andcommunicates by means of a pipe, k, with branch 1 of a threeway cock, Z,or other suitable regulating threeway valve, branch 2 of which is opento the atmosphere, and branch 3 communicating with the steam-chest b bymeans of pipe m. The plug of the three-way cock Z may be 0perated by thehand-wheel n, or by levers and rods, as found most suitable. Thethree-way cock Z being adjusted so that branches 1 and 2 are incommunication, and air thereby admitted from the atmosphere through pipek into the cylinder d above the balancing-piston e, the engine isstarted, and as the slide-valve a reciprocates the balancing-piston e isalso reci procated and adj usted to the varying positions of theslide-valve a by the connectingrod f, any resistance to the movement ofthe piston e by the expansion or compression of `the air on its otherside being prevented by the free inlet or exit of the air through thethree-way cock Z and pipe 7c.

An equilibrium is obtained between the steam-pressure on thebalancing-piston @and the pressure of steam less the back-pressure onthe slide-valve a by observing the following formula: The area of theslide-valve in square inches multiplied by the pressure of steam persquare inch, minus the area of the exhaust-space beneath the slide-valvemultiplied by the back-pressure, is equal to the area of thebalancing-piston e. When the ICO ) slide-valve a, steam may also beadmitted Y comotive slide-valve, Where the Vback-pressure steam is'shut-off from the steam-chest b and I the slide-valve c is. being movedby the mo` mentum of the engine, air :may be admitted 'to thesteam-chest b by moving the three-way cock Z so that branches 2 and 3and pipe m are in communication.

In case of the lifting or displacement of the from the steam-chestb tothe cylinder d, above the balancing-piston e, by moving the threewaycock Z so that branches l and 3 and pipes k and m are in communication,the effect of this being to return the slide-valve a to its properposition.

In the illustration of our invention shown in Fig. et, which isspecially adapted to a loon the slide-valve a is constantly varying, avalve, o, is fitted in the exhaust-passage p and loaded to a normalback-pressure by means ot a spiral spring, q. The chamber of this valveo communicates with the space above the balancing-piston e by pipe 1^,so that When the back-pressure on the-slide-valve a exceeds that towhich the valve 0 is loaded the valve o opens, and, admitting steamabove the balancing-piston e, causes the pressure on the latter tocounterbalance the excessive back-pressure on the slide-valve a. In thiscase the inflowing steam through pipe a" to the space above thebalancing-piston e is prevented from escaping through the three-way cockZ into the atmosphere by a spring-Valve, s, which is itted Yat andclosed over the mouth of branch 2 of the three-Way cock Z by thepressure of the steam unt-il the balance of pressure on the slide-valvea is restored, when'the valve s will be opened by its spring, and freepassage of air given through the three-Way cock Z, as before.

We claim as our invention 1. The combination, with a slide-valve and abalancing-piston, of a port or passage leading from the exhaust to thecylinder of the balancing-piston, and a loadedvalve, substantially asand for the purposes specified.

2. Ihe combination, with a slide-valve and its balancing-piston, of thelugs h, provided with bolts, packing-strips '13, rod or pin g, andconnecting-rod f, substantially as and for the purposes specified.

3. In a steam-engine balancing slide-Valve, the combination ofbalancing-piston e, connected with slide-valve a and Working in cylinderb, a pipe or passage leading to the cylinder of the balancing-piston, apipe or passage leading to the steam-chest, and three-Way cockcommunicating with the atmosphere, substantially as shown, and for thepurpose described.

4. In a steam-engine balancing slide-valve, the combination ofbalancing-piston e, connected with slide-valve a and Working in cylinderb, Valve o, pipes i k, three-way cock Z, and spring-valve s,substantially as shown, and for the purpose described. y

In testimony whereof we aix oursignatures,

in presence of ltwo witnesses, this 13th day of December, 1886. l

WILSON W. PRIMM. JEAN B. PRIMM. Witnesses:

S. L. SCHRADER, Louis D. PICOT.

